By the time Europeans arrived in North America and marveled at the resources they found, human beings had been living amid the continent's bounty for at least 11,000 years.

While the ecological havoc wrought by European settlers has been well documented, questions about how well the original inhabitants managed natural resources have been debated for decades. Now some answers are emerging.

In "The Day Before America," a recently released story of the continent from 18,000 years ago to the present, environmental writer William MacLeish paints the clearest portrait available of the dramatic shifts in climate and ecology that swept North America during the prehistoric period and of how Native Americans adapted to them.

Customs and lifestyles varied, but MacLeish gives moderately good marks to the way most tribes interacted with the flora and fauna around them. Although the Iroquois were fierce hunters, he points out, they also harbored a respect for deer and other prey that may have prevented overhunting.

In the western areas where bison were common, trapping techniques showed increasing levels of sophistication -- and, perhaps, sensitivity. Crude, early methods killed the animals in large numbers -- for example, by setting fires to drive them off cliffs. But the hunters later devised ways to herd them down trails and into corrals. And when bison populations began to decline, according to the author, there is some evidence that the hunters may have limited the number they killed.

MacLeish cites the Archaic period (or Middle Stone Age), which in the eastern part of the continent began about 10,000 years ago and ended about 3,000 years ago, as a time when the Native Americans lived in closest harmony with their environment. Women collected rabbits, opossums, berries and greens. Men hunted bear and elk. The massive drives resulting in the slaughter of hundreds of wildlife, common in the the southern and western regions, were not conducted in the eastern part of the continent. This way of life, concluded MacLeish, was "perhaps the most sustainable that humans have developed so far."

Part of the Natural World

The religious beliefs and traditions of many tribes encouraged the view that humans were part of the natural world, rather than its masters. The Iroquois, for example, viewed other living creatures as possessing qualities of humanness and even kinship. And in plant-animal relationships a certain reciprocity was implied, according to George Hamell, a specialist on the tribe at the New York State Museum in Albany.

Hamell said the Iroquois expected that if a hunter killed more deer than needed, he would be punished for it.

The most dramatic ecological changes in prehistoric America had nothing to do with human activity, by MacLeish's account. About 12,000 years ago, the ice age gave way to warmer temperatures, and melting glaciers shaped the continent's major bodies of water. Meltwater tumbled down the St. Lawrence Valley, creating a river that flowed out to the Atlantic. The retreat and rebound of glaciers gashed the earth, forming inland water bodies, including those along the border with Canada that we now call the Great Lakes.

About the same time, forests began to spread in all directions. Ponderosa pines expanded from the South to the Rockies. Hickories, a midwestern native, moved north and then east. Oaks, at first common in the Mississippi Valley, gradually crept toward New England. With the help of pigeons, blue jays or other carriers, which transported their seeds, the oaks marched eastward at the rate of about 1,000 feet a year, by MacLeish's calculation. At that pace, it took oak forests five millennia to advance 1,000 miles.

Horses, Bison and Bears

During the period from 12,000 to 10,000 years ago, the mammalian life on the continent would have done Noah's Ark proud. In what is now the Appalachian Valley of West Virginia and Pennsylvania, for example, more than 75 species of mammals roamed, including three types of bear, five now-absent members of the deer family (among them stag moose and caribou), two kinds of bison, ground sloths, armadillos and mastodons.

Horses were probably originally native to North America. By 1492, however, they had flourished, migrated to Asia and fallen into extinction on this continent, only to be reintroduced by European explorers.

For MacLeish, Native American agricultural practices indicate a particular environmental sensitivity. For example, about 4,000 years ago midwestern people adapted a gourdlike vegetable called the cucurbit to their needs. They apparently employed it as a utensil at first, then developed it into a variety of edible squash.

More than 3,000 years ago, the people of the Cumberland Valley in what is now eastern Kentucky apparently responded to animal shortages by creating gardens. Drawing on the work of Wes Cowan, a Cincinnati anthropologist, MacLeish described how the natives grew plants that had originated thousands of miles to the west, such as sunflower, goosefoot and sumpweed. They may have used seeds found in the feces of migrating animals. In a region where the supply of wildlife varied with the seasons, the gardens almost certainly were an important food supplement.

In about the same period, Anasazi natives in the arid region of northwestern New Mexico were responding to water shortages by constructing elaborate irrigation systems. When rain fell, water poured off cliffs and into flumes at the bottom of canyons. A side canyon would dump water into man-made ditches, which in turn would deliver it to stone-lined distribution boxes. The local people would thus have water enough to sustain corn or other crops.

Far From Perfect

But the Native Americans' environmental record was far from perfect.

In the Northeast, they burned forests to force out elk and deer, creating gusts of hot wind, soot and smoke powerful enough to make October feel like July. People in the region also created elaborate devices to drive herds of white-tailed deer into enclosures in the forest, where they were slaughtered.

In the Great Plains, some tribes drove bison over cliffs, creating heaps of fur and flesh far greater than their needs. Mounds of remains, discovered by archaeologists at the foot of cliffs, show that many bison were left to rot.

There is also evidence from bones, MacLeish points out, that before Bison antiquus became extinct, the species suffered stress that may well have been caused by overhunting.

However brutal, such acts pale in comparison to the assaults Europeans would later launch on the continent's resources. The beaver population was among the first to suffer. French and Dutch traders took 30,000 beaver pelts in 1620 and almost 300,000 in 1690.

The forests were also early casualties. After the arrival of settlers, MacLeish concludes, "the Midwest went bald in a human lifetime."